Check that you do not have a filter enabled in Outlook. First change the view in Outlook to one that lists the items. Then right click within the right hand pane and select Filter…, click Clear All, and click OK. You may need to change the view in order to display all items.

If a client does not see one or more shared folders to which they have been given access, check that access permissions have been correctly set in the Administrator. If permissions are correct, open Outlook and search for the shared folders under the Shared Information folder while in the Folder List view, as described in this FAQ: I cannot see the Shared data in Outlook..

In an Outlook client where shared data is not seen correctly, delete the Shared Information folder. Then remove this from the Deleted Items folder. Re-synchronize, to download a fresh copy of all shared folder data from the server to the Outlook client.

In an Outlook client where data are not shared correctly (as would be the case when all other Outlook clients persistently see the data incorrectly), click Tools, Share, Settings and un-share the folder(s). Re-synchronize to propogate those changes. Then share the folders once more and synchronize again. This removes the shared data from the server and then re-shares it. (NB. After this step the permissions must be re-assigned to these folders in the Administrator so that other users will have access once more).

Resolve any Add-In conflicts. Disabling all Add-Ins except those required by WorkgroupShare will confirm this, you can then enable the other Add-Ins you need, later. For more information see the FAQ How do I resolve Add-in Conflicts?.